Telephone-exchange trunking system.



T. G. MARTIN. TELEPHONE EXCHANGE TRUNKING SYSTEM.

APPLICATION EILED D EC- I0. 1910.

Patented Dec. 28, 1915.

5 SHEETS SHEET 1.

T. G.' MARTI N.

TELEPHONE EXCHANGE TRUNKING SYSTEM.

APPLICATlO N FILED DEC 10. I910.

Patented Dec. 28, 1915.

5 SHEETS-SHEET 2- T. G. MARTIN- TELEPHONE EXCHANGE TRUNKING SYSTEM.

APPLICATION FILED DEC. 10, 1910.

- Patented D60. 28, 1915.

s SHEETS-SHEET 3.

T. G. MARTIN. V TELEPHONE EXCHANGETRUNKING SYSTEM V APPLICATION FILED DEC-10, I910. 11,165,69U Patented Dec.28,1915..

g amo 'gdaim T. G. MARTIN. v

TELEPHONE EXCHANGE TRUNKING SYSTEM.

APPLICATION FILED DEC. 10, I910.

ilmm m v Patented 1960.28, 1915.

5 SHEETS-SHEET 5.

TALBOT G. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNUR TO AUTOMATIC ELECT COMPANY, OF CHIAGO, ILLXNOIS, A CORPORATION OF ILLINOIS.

TELEPHONE-EXCl-IANGE TRUNKING SYSTEM.

Specification of Letters Patent.

Patented D co,

Application filed Becember 10, 1910. Serial No. 596,710.-

To all whom it may, concern:

Be it known that I, TALBOT G. MARTIN, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvement in Telephone-Exchange Trunking Systems, of which the following is a specification.

My invention relates to telephone exchange systems in general.

It relates more particularly to semi-auto matic telephone exchange systems of the kind in which two-way trunk lines are em ployed, and more especially to systems of this kind in which the subscribers telephone lines are of the manual type, being provided with the customary manual equipment only at the substations, and terminatingin a manual board, or in means for establishing con nection with a manual board. In this respect my invention is in the nature of an improvement on my co-pending application Serial No. 316,74l2, filed May let, 1906.

It also relates to systems of the kind in which provision is made for repeating switch-operating impulses from one section of the line circuit to the other, as issometimes necessary in extending connection from one exchange to another, or from one telephone line to ,another in situ ation where it is desirable to transmit the original impulses over the entire circuit. The repeating mechanism herein disclosed is in the nature of an improvement on the repeater disclosed in my copending appli cation Serial No. 507,210, filed July 12, 1909.

Objects of my invention are to provide an improved construction and arrangement whereby, in a semiautomotic system of the above-mentioned general character, the same trunk lines may be used for-calling in opposite directions between a main exchange and a branch exchange, thus obviating" the necessity of having one set of trunks for c-al 'ng into the manual board at the main exchange, and another set of trunks for calling out or in the opposite direction; to provide an improved construction and arrangement whereby a two-way trunlr may terminate. at one end in a numerical switch. and may have the same end connected with a non numerical switch, the first switch being operative to extend connection from the trunk' there being also means at the other the trunk line for extending connecti thereto and therefrom; to provide ani proved construction and arrang. whereby two-way trunks may be cm, .i' between subscribers line switches manual board, or between subscribe numerical line switches and a swit of any suitable character, whereby con tions may be made to and "1'om the subscribers lines over the same trunks; t I vide an improved construction and a1 ment whereby an automati switch b v a calling subscriber and a manual bo rd a which the call is answered may be automatically released by the withdrawal oi the answering plug from the jack of the tru; I over which the connection is established from the automatic switch to the manual board to provide an improved construction and arrangement whereby, in a semi-automatic system of this general character he automatic switch between the calling scriber and the manual board may i.- leased by the hanging up of the receive the calling substation-that is 'to say, wo by this may be done only when the ope has withdrawn the plug, as previrnu stated, or when the subscriber hangs up fore the operator has answered; and to vide an improved construction and arrangt ment whereby a repeater in a two-wire tem is operative to disconnect or cut oil bl e condensers thereof to prevent the fr" remaining in the line circuit while the. pulses are being repeated. over one seen thereof to another.

it is also an object to provide certain tails and features of improvementand com binations tending to increase the ability of a tGlGDllOIlQ exchange sy cm this particular character. As will hereinafter more full appcrm my vention relates in some Measure what'is ordinarily known as a two-wire temthat is tosa'y, an automatic or automatic system in which certain or switches are controlled over the two of the line circuit in series, as distingu from other systems in which t switches are operative or controll grounding first one side and thenthe or" the ground circuit leading thex which latter system is ordinarily in a three-wire system It will also be seen that my invention relates to a system of this kind in which the current for both switching and talking purposes is supplied from a central source, or from several central sources, a system'of this kind being ordinarily known as a common battery system.

In the accompanying drawings Figures 1 and 2 taken together represent a complete connection between a calling substation A (Fig. 1) and a called substation A (Fig. 2), and also means whereby the substation A may call substation .A, in a system embodying the principles of my invention. The apparatus shown in Fig. 1 is situated in a branch exchange, while Fig. 2 represents a portion of a distant manual exchange. Figs. 3, 4 and 5 show the central office switching apparatus by means of which the manual substation A may obtain'connection with the automatic substation A (Fig. 5) by passing through an intermediate automatic exchange represented in Fig. 3 and a portion of Fig.- 4.

The manual substations A and A may be of any suitable or approved type. As shown, the substation A comprises the usual receiver 2, switch hook 3, transmitter 4, in-

duction coil 5, ringer 6 and condenser 7. The ringer 6 and condenser 7 are perma nently bridged across the line conductors 9 and 10. The circuit through the transmitter 4 is normally open, but when the receiver is removed from the hook, the said hook engages the contact point 8, bridging the transmitter 4 across the line conductors in series with the primary Winding of the in duction coil'5. The line conductors 9 and.10

in magnet 20 which has an armature 21 pivare connected to an individual switch C at the branch exchange. 7

Theindividual or line switch C is of the general type disclosed in British Patent #26,301 of 1906, and in the Western Electricz'an of Chicago, Illinois, of January 25, 1908. The switch C is provided with a pulloted at the point 22. To the opposite end of the armature '21 there is attached a plunger (not shown) adapted to force springs 23, 25, 27 and 29 into contact with I springs 24, 26, 28 and 30, respectively. The

. energizing circuit of the magnet 20 is controlled by the calling subscriber through the medium of the relay 81. The plunger arm 21 is provided with a small projection 36 which operates when said arm 21 is attracted to' separate springs 32 and 34 from the The springs 33 and 35, respectively. springs 32 and34 may also be operated by the cut-ofi' relay 37. Although only one set of springs 23, 24, 25, 26, 27, 28, 29 and 30 a is shown, eacli switch C is in reality provlded with a bank comprislng a number of such sets of springs, each set forming the terminals of a two way trunk line between the two exchanges. Each trunk is multipled through the corresponding bank springs of a group of switches controlled by the master switch D.

The master switch D is also of the general type shown and described in the said British patent and Western Electrician. Among other details the master switch comprises a ratchet wheel 38, a motor magnet 39, a motor magnet relay 40 and a bank of contacts comprising a common segment 43 and a number of individual segments a. The ratchet wheel 38 is connected to a shaft (not shown) with which the plungers of the idle line switches normally rest in looking err gagement. The connection between the wheel 38 and the plunger shaft is such that arotary motion of the wheel gives to the shaft a reciprocating motion to move the idle plungers from a position in front of one trunk to another. The wheel 38 is actuated by the magnet 39 throughthe medium of the armature .41 and pawl 42. The wiper 44' is secured to the plunger shaft and is adapted to always keep some one of the individual segments a in electrical connection with the common segment 43. Secured to the ratchet wheel 38 there is anotched wheel 45, made preferably of insulating material, which controls a pair of springs 46 and 47. The notches in the wheel 45 are so spaced that the springs 46 and 47 may disengage only when the plungers that are engaged with the plunger shaft are in a position directly in front of the bank terminal of a trunk. When a line switch operates, its plunger engages thexbank springs of the idle trunk in front. of which it is being held by the plunger shaft. The motor magnet relay 40 is accordingly energized through the wiper 44. This relay operates to close the circuit of the motor magnet 39, which then operates to rotate the ratchet wheel 38, and the notched wheel 45 is moved far enough to .force springs 46 and 47 into engagement, which furnishes a new energizing circuit for the motor magnet 39. The motor magnet 39 will thus continue to operate until the idle plungers are directly opposite the terminals of an idle trunk. When this position is reached the springs 46 and 47 separate, and as the master switch wiper 44 has been moved to a position corresponding to the terminals of said idle trunk, the relay 40 becomes deenergized and opens the circuit of the operating magnet 39.

Each of the trunks to which the lineswitch C has access is provided with a relay48, 48, etc., of which only the ones he longing to the first and last trunks are shown. Each of these relays is adapted to be energized whenever the trunk to which through the relay 49, which in turn operates to disconnect the relay 40 from the com'inoii bank segment 43 and to cause the battery to be disconnected from the relay 31st all the line switches O to prevent the operation of said switches when all the trunks are busy. The plungers of the line switches C are selfalining-that is, when a plunger is released from its operated position it immediately returns to locking engagement with the plunger shaft, thus assuming a position in front of the terminal of the same trunk before which all the other idle plungers are resting.

The connector F is of the general type disclosed in United States Letters Patent No. 815,176, granted March 13, 1906, to Keith; Erickson and Erickson. Among other details the connector comprises the' wipers 68, 69 and 70 secured to a shaft (not shown) which .has a vertical motion controlled by the vertical magnet 71 and a rotary motion controlled by the rotary magnet 72. The operation of the connector is controlled by the calling operator through the medium of the double-wound line relay 73. The side switch, composed of the wipers 7 1, 75, 76, 77 and 222, is controlled by the private magnet 78 in a well-known manner. The circuit of the private magnet 78 is controlled by the relay 7 9. The relay 79 and release relay 80 are slow acting relays that is, slow to deenergize after their ener gizing circuits have been 'broken. The means for releasing the switch is provided in. the release magnet'81. The release magnet 81 is disconnected from battery by the separation of the off normal springs 82 and 83 as long as the switch shaft is in its low, est position. As soon, however, as the shaft is raised one or more steps the arm 5 1 permits the springs 82 and 83 to engage to connect the magnet 81 with the battery B. After a connection is completed the ringer relay 84 operates to connect the generator I with the called substation. After the receiver is removed from the hook the called substation is provided with talking battery current through the back-bridge.relay 85. The high resistance relay 56 provides means whereby the operator may obtain supervision of a call through the connector F.

The two-way trunk 86 and 87, besides terminating in the bank contacts of the line switch C, is also connected to the connector F through the springs of the relay 88.

This two-way trunk terminates in the main exchange in the ack, 7'. When the trunk is used to extend a call from the branch to the main exchange the relay 88 operates to disconnect the connector switch F from the "trunk conductors.

The operators cord circuit 0 comprises the supervisory relays 89, 90, 91 and 92, lampsQB and 91- and keys K, K and K. The circuit through the cord is divided into two parts by the condensers 95 and 96. The operators talking set S is similar to the ordinary operators used in manual systerns, with the addition of a calling device consisting of the impulse springs 97 and 98 and the impulse wheel 99. When the impulse wheel is rotated forward the springs 97 and 98 are not operated, but as the impulse wheel returns to normal position the springs 97 and 98 are separated a number of times, depending .upon the digit to be alled. ll ith the talking set S there is associated a key K by means of which the receiver may be short-circuited when the call.- ing device is being used.

The lines of the substation A terminate in the jack j.

The line switch C, which is allotted to the jack j of the manual exchange, is the same as that disclosed in the Western Electrio ion of January 25, 1906, referred to above, with the exception of a slight change in the circuit connection which renders the switch C operable by simply closing the line circuit. The plunger of the line switch C is normally held out of the bank against the tension of a. spring; lVhen the magnet 100 is energized it unlocks the plunger, al lowing it to be forced into the bank by said spring. if, after the line switch has been operated, the release magnet 101 is energized it places the apparatus in such a. position that the plunger will be withdrawn from the bank by a spring upon the following deenergization of the magnet 101., The trunks from the banks of the line switch C lead to first selector switches E. The group of line switches of which the switch C is a member is controlled by a master switch D, which is like the master switch D.

The first selector E is of the general type disclosed in United States Letters Patent No. 815,321, granted March 13,- 1900, to Keith, Erickson and. Erickson, but is slightly modified to operate in a two-wire system that is, in a system in which no ground connection is used at the substation. or in which the swtiches are controlled over the two sides of the line circuit in series. Among other details the selector 10 comprises a of wipers T102, 109 and 10L carried upon a shaft (not shown) which has a vertical motion controlled by the vertical magnet and a rotary motion controlled by the rotary'magnet 100. The operation of than by its de'nergization as shown in the said selector patent. The selector E is also provided with a bank of contacts adapted'to be engaged by the wipers 102, 104 and 103, and to at least a part of which are connected trunk lines leading through repeaters R to selector switches H of a distant exchange.

The repeater R is provided for .the purpose of repeating impulses to the switches of the distant exchange. The repeater is provided with a double-wound line relay 114 which is similar to the line relays of the selector and connector switches. During the time the repeater is operating the calling line is disconnected from the trunk by the slow acting relay 115. The slow acting relay 116 maintains an energizing circuit for the release relay of the selector E after it has operated. The talking circuit through the repeater is divided into two parts by the condensers 117 and 118.

The selector H is'similar to the selector E and the connector F is similar to the connector F with the omission of the supervisory relay 56.

At L is shown a busy signaling machine and at I a ringing current generator is shown.

The line switch G which is individual to the line of substation A is like the line switch C.

The automatic substation A may be of any approved type. As herein represented, the substation A comprises the usual receiver 119, switch hook 120, transmitter 121, induction coil 122, ringer 123, condenser 124, impulse springs 125 and 126 and impulse wheel 127. The switch hook 120 controls the substation circuits through the medium of the cam arm 128 and springs 288, 289 and 290.

As shown, each exchange is provided with a battery, having one terminal grounded, to

" provide current for talking and for operating the switches.

In order to give a clearer understanding of my invention I will now explain theoperation of the various apparatus em ployed when the subscriber A calls subscriber A and when subscriber A calls either subscriber A or subscriber A.

V hen the leceive at substation A is removed and the hook 3 engages the contact point 8, a. circuit is closed through the slowacting line relay 31 of the line switch C. This circuit extends t'rom ground G through the springs 32 and line conductor 10, transmitter -l-. primary winding of the induction coil 5. contact point 8, switch hook 3, line conductor 9, springs 35 and 34, relay 3 1, springs 130 and 131 to the battery lead 133, thence through the battery B to ground G. The relay 31, upon energizing, closes a circuit extending-from ground G through the springs 129 and 129 and pull-in magnet 20 to the battery lead 133. The magnet 20, upon energizing, operates to force the plunger into the bank and to separate the springs 34' and 32 from the springs 35 and 33, respectively, whereby the circuit of the relay 31 is broken The relay 31 being slow to deenergize maintains its springs in contact until the relay 134has had time to close a new holding circuit through the magnet 20, as will be explained later. When the bank springs 29 and 30 are pressed into engagement by the plunger of the line switch C an energizing circuit is closed through the relays 88, 48 and 40. This circuit extends from ground G through bank springs 29 and 30, relay 88, thence one branch passes through relay 48 to the battery lead 133, and another branch passes through the contact point 136, master switch wiper 44, bank segment 43, relay springs 137 and 138 and relay 40 to battery lead 133. The relay 88, upon energizing, operates to disconnect the connector F from the trunk conductors 86 and 87 and to connect the relay 134 with the conductor 86. The energization of the ground G through relay 139, springs 140 and 141, and from groundGr through the magnet 39 to interrupter springs 142, and through springs 143 and 144 to battery lead 133. Since this circuit includes the inter rupter springs the magnet 39 operates in a manner similar to that of a buzzer to rotate the ratchet wheel 38 and advance the idle plungers to an idle trunk. As soon as the wheel 38 is advanced one step the springs 46 and 47 are forced into engagement by the wheel 45, thereby maintaining the operating circuit of the magnet 39 independent of the relay 40. The magnet 39 will thus continue to operate until the spring 47 drops into the next teeth of the wheel 45, at which time the plunger-s will have reached a position directly in front of the terminals of the next trunk after the one just seized, and the wiper 44 will ha \e left the contact 136 and allowed,

the relay 40 to deenergize. Since the relay 40 is deenergized and the springs 46 and 47:

wiper 44 would have found a guarding potential upon the correspondingbank con-.

tact, the relay 4Q would have remained energized when the "springs 46 and 47 were separated, and the magnet 39-would have contiuuedto advance the plunger-s until an incense controlled by the master switch I), and connects a busy signaling machine with the idle lines. The spring 132 of vthe relay 139 is connected with a busy signaling machine similar to the busy signaling machine L (Fig. With this arrangement it is impossible to operate a line switch C while its plunger is being moved from one trunk to another, and any subscriber attempting to make acall at that time will receive the busy signal.

When the bank springs 23 and 25 are pressed into engagement with the springs 2st and 26, respectively, by the line switch plunger the line conductors'9 and are :-:tended to the main exchange over the trunk conductors 86 and 87, and a circuit is losed through the relays 134 and 291. This circuit extends from ground G l Fig. 5) through contact point 292 and armature 293, and over trunk conductor 87 and line co ductor 10, to and through substation A and back over line conductor 9 to trunk conductor 86, from which one branch passes through relay springs'1l6 and 145 and relav 13st to the battery lead 133, and another nch passes over the trunk to the main exchange and through armature150, conpoint 151 and relay 291 tobattery lead The battery lead 133 is common to all trunks leading from the exchange of The relay 291, upon energizing, op- .s to close a circuit from ground G" through the lamp 152 to battery'B to signal e operator. The relay 13 1, upon energizcloses a holding circuit through the net before the relay 31 has time to energize, as before stated. This circuit and 155, bank springs 28 and 27, relay and magnet 20 tothe battery lead 132'. he relay 134:, in its energized position, also ipplies a guarding potential from ground over the private normal conductor 156 to the private bankcontact 294: of all the connectors which have access tothe line of substation A. This guarding potential protrots the calling line from interference over the connectors. The operator answers the signal of the lamp 152 by inserting the plug j into the jack j and throwing the key K to bridge the operators set it across the cord. llhen the plug 71 enters the jack t w prings 157 and 1:38 are forced into enenicnt to close a circuit extending from ground G through the cutoff relay to the battery B. The relay 159, upon ten from. ground G through the springs energizing, operates to attract its armatures 150 and 293 out otengagement with the con tact points 151 and 292 and into contact with points 160 and 161, respectively. The separation of the armatures from points 151 and 292 opens the circuit through the relay 291, which denergizes and allows the lamp 152 to be extinguished. When the arinatures 1'50 and 293engage the contact points 160 and 161, the trunk is connected with the cord and the calling substation is provided with talking battery current over a circuit ertending froin'ground G through supervisory relay 90, tip conductors v0t plug p and jack 3', trunk conductor 86, line 9, through the primary winding and transmitter of substation A andover line 10, trunk 87, armature 293,,contact point 161, sleeve conductors of jack y and plug 79 and relay 92 to battery 15". A branch circuit also extends from conductor 86 through relay 13a to maintain it energized, but the said relay has a high resistance so as not to impair the talking efliciency.

Upon learning the number of the desired substation the operator'restores K inserts the plug p into the jacket 7" of the desired line and throws the key K to shift the springs 162 and 163 out of engagement with springs 16 1 and 165 and into contact with springs 166 and 167, respectively, whereby the calling llIlt' is disconnected from the cord and a ringing current generator is bridged across the called line. The engagement of springs 166 and 162 also closes an energizing circuit through the cut-oil relay 168, said circuit extending from ground Gr through springs 166 and 162, tip conductors of plug 1' and jack j and'relay 168 to battery B. The relay 168, upon the energizing connects the line of substation A with the jack j. The path of the ringing current for the substation A extends from. ground G through key springs 166 and 162, tip of plug 37 and jack j, relay springs 169 and 170, line 171, condenser 172, ringer 173, line 17%, relay springs 175 and 176, sleeve 01 jack j and plug key springs 163 and 167 and through generator (not shown) to ground. After ringing the called substation the key K is restored to normal position, completing the connection between calling and called lines. After the key 1: is restored the relay 168 remains energized over a circuit extending from ground G through the supervisory relay S9, springs 17? and 178 of key K, springs 161 and 162 of key K and through relay 168 to battery. The relay 39, which is included in this circuit, is also ener ized and operates to close a. circuit from ground G through the lamp 93 and baclr contact of the relay 91 to battery. llhen the called subscriber removes the receiver the substation A is provided with talking" current from th battery B through the relays 89 and 91, and the two subscribers may converse over the heavy conductors shown in Figs. 1 and 2. The relay 91 is energized by the talking current and operates to open the circuit of the lamp 93.

After the conversation is completed the.

operator is given the disconnect signal in the following manner: The restoration of the receiver at the called substation opens the energizing circuit of the relay 91, which deenergizes and again closes the circuit of the lamp 93. The restoration of the receiver at the calling substation destroys the energizing circuit of the relay 92, but the relay 90 remains energized in series with the relay 134. The denergization of the relay 92 closes the circuit through the lamp 94. The simultaneous glowing of the lamps 93 and 94 signifies to the operator that both subscribers have hung up' their receivers, and that the plugs 79 and 70 may be remover? from the jacks. The removal of the plug from the jack 7" breaks the circuit of the relays 89 and 168' The relay 89, upon deenergizing, breaks the circuit of the lamp 93. The removal of the plug p from jack j breaks the circuits of the relays 90, 159 and 134. The relay 90, upon deenergizing, breaks the circuit of the lamp 94. The relay 159 disconnects the trunk from the jack 7' and restores the relay 291 to the trunk. The relay 134, upon denergizing, removes the guarding potential from the calling line and breaks the holding circuit of the line switch magnet 20. The magnet 20, upon deenergizing, allows the plunger to be withdrawn from the bank and the line switch C to be again connected with the line. The withdrawal of the plunger allows the relays 48 and 88 to deenergize, the latter operatingto reitore the connector F to the trunk 868 When the subscriber at substation. A wishes to call substation A the operation is as follows: The removal of thereceiver at the'substation A closes a circuit through j the relay 179. This circuit extends from ground G through contact point 180, armature 175, line 174, transmitter and primary winding of substation A, line 171, armature 170, contact point 180 and relay 179 to battery B. The relay 179, upon energizing,

closes a circuit through line lamp 181. In answer to the signal of lamp 181 the operator inserts the plug 0 into the jack 5 and operates the-key K to connect the talking set S with the line. The insertion of plug 79 into jack 7" closes an. energizing circuit through the relays 90 and 168 in series. The relay 168, upon energizing, destroys the circuit of relay 17 9 and connects the line with the plug 1;, whereupon the calling substation is provided with talking current from battery B through relays 90 and 92. The re- -to the branch exchange.

lay 92 is also energized by the talking current. Upon learning the number of the desired substation, which is assumed to be 20, I

the operator restores key K inserts plug 7) into jack j and operates key K to connect springs 178 and 182 with springs 183 and 184, respectively. The operation of key K disconnects the cord from the trunk and bridges the operators set S across the trunk.

As soon as the key K is thrown, an energizing circuit is closed through the line relay 73 of the connector F.

springs 189 and 190 and relay to battery.

lead 133. The relay 80, upon energizing, shifts spring 192 out of engagement with spring 193 and into contact with spring 194, and closes the contact between springs 195 and 196. The engagement of springs 195 and 196 establishes a guarding potential at the master switch bank contact 136, and closes a circuit extending from ground G through said springs over conductor 197 and through relay 48 to battery lead 133.

This circuit ex-. tends from ground Gr through side switch' It is thus evident that the relay 48 is energized whenever the trunk to which it belongs is in use, regardless of whether the call goes from the branch exchange to the main exchange, or 'from the main exchange When all the trunks are in use at one time all the relays 48 to 48, inclusive, will be energized and close a-circuit from ground G through the relay 49 to battery-lead 133. The relay 49, upon energizing, shifts the spring 140 out of engagement with the spring 141 and into engagementwith the spring 198, and forces the spring 138' out of engagement with the spring 137. The disengagement of the springs 137 and 138 disconnects the relay 40 from the bank segment 43 topreventthe operation of the master switch While all the trunks are busy. The engagement'of the springs 140 and 198 closes an energizing circuit through the relay 139, which opefates to disconnect the battery from the line switch relays 31. As soon as any trunk becomes idle its relay 48 deenergizes and. opens the circuit of the relay 49, .WhiClPiestores the master switch circuits to normal condition.

When the operator operates her callingdevice for the first digit (2') of the desired number, the impulse springs 97 and 98 are.

separated twice, thus twice breaking the cir: cuit of the connector line relay 73. During the operation of the calling device the key K may be operated to short-circuit the receiver to prevent the impulses frompassing through it. Each time the circuit of the relay 73 is opened, the said relay deenergizes, momentarily opening the circuit of the relay 80 and allowing the springs 189 and 191 tocome into engagement. The relay 80 is slow to deenergize, and this momentary opening of its circuit is not suiticient to'allow it to restore to normal position. The engagement of the springs 189 and 191 closes an energizing circuit extend ing from ground G through the springs 189 and 191, 192 and 194:, private magnet relay 79, vertical magnet 71 and side switch Wiper 77 to the battery lead 133, thence through the battery B to ground G. The

vertical magnet receives two impulses over the circuit just traced, and operates to raise the shaft and wipers 6,8, 69 and 70 two steps to a position opposite the second row or level of bank contacts. As soon as the shaft leaves its lowest position the arm 541 permits the springs 82 and 33 to engage and connect the release magnet 81 with bat tery. The relay 79 is energized by the first impulse to the vertical magnet, but being a slow-acting relay does not have time to deenergize between impulses. The relay 79, upon energizing, closes a I circuit from ground G through the springs 199 and 200 and private magnet 78 to the battery lead 1'33through the springs 83 and 82.

After the last impulse is delivered to the vertical magnet the relay 79 has time to deenergize and open the circuit of the private magnet 78. The private magnet 78 then in turn deenergizes and permits the side switch to pass from first to second position. The movement of the side switch wiper '77 fromfirst to second position shifts the battery connection from the vertical magnet 71 to the rotary magnet 72. Now, when the calling device is operated for the lastdigit the line relay 73 operates in the same manner as for the first digit, but in this case the engagement of the springs 189 ,and 191 closes a circuit through the rotary magnet 72. This circuit extends from ground G through the springs 189 and 191, 192 and 194, private magnet relay 79, springs 201 and 202, magnet 72, contact point 203 and side switch wiper 77 to the battery lead 133. Since the last digit is 0 the rotary magnet receives ten impulses over the circuit just traced, and operates to rotate the wipers ten steps onto the contacts of the desired line. The private magnet relay 79 is again energized by the first of this series of impulses and again closes the circuit of the private magnet 78. After the last imment of the sideswitch wipers 74- and 75 with their third-position contact points completes the connection between the call ing and'called lines. The engagement of the wiper 77 with its third-position contact point closes a circuit extending from ground G through the interrupter 204E, springs 205 and 206, ringer relay 84: and side switch wiper 77 to battery lead. 133. Since this circuit includes the interrupter 20% the ringer relay 8 1 is energized intermittently. Each time the relay 8% is energized it operates to disconnect the calling and called lines, and bridge the ringer generator 1 across the called line. Thus the bells 6 at substation A will be rung intermittently as long as the circuit through the relay s4 and interrupter 20-1 is maintained.

When the side switch wiper 222 engages its third-position contact point 213, the relay 73 is connected to ground G through the high resistance supervisory, relay 56. Also, as soon as all the impulses have been delivered for the last digit the operator restores key K, thus closing circuits through the supervisory relays 89 and 91. The circuit through relay 91 extends -from the nongrounded terminal of battery B (Fig. 2) through said relay, normally closed springs of keys K and K, .sleeve conductors of plug p and jack j, trunk conductor 87, springs 149 and 148 of relay 88, conductor 186, winding 185 of relay 73, side switch wiper 222 and relay 56 to ground G.

Since this circuit includes relay 56, suffi of plug p and jack y', trunk conductor 86, iii

springs 146 and 147, conductor187, and winding 188 of relay 73 to battery lead 133, thence through the battery B to ground G. The relay 89, upon energizing, closes a circuit through the lamp 93 and battery B. In order to prevent the deenergization oi the connector release relay 80 in case the relay 73 should allow its armature to drop back when the relay 56 enters its circuit, the relay 5G is provided with a couple of springs 21 and 215, which maintain the circuit of the relay 80 as long as the circuit of the relay 56 is closed.

lVhen the 'callcd subscriber removes his re .ceiver from the switch hook, or as soon thereafter as the relay 8 L deenergizes, the called substation is provided with talking current over a circuit extending from grouml G through the side switch wiper 78, winding 207 of the relay 85, ringer relay springs 209 and 210, side switch wiper 75, wiper 70, conductor 211, line 10, transmitter 4, primary winding of the induction coil 5, line 9, conductor 212, wiper 68, side switch Wiper 74, ringer relay springs 213 and 214, and winding 208 of the, relay 85 to the battery lead 133. Since both windings of the relay 85 are includedin this circuit, this relay becomes energized and operates vto separate the springs 205 and 206, and to press the springs 216 and 217 into engagement with each other. The separation of the springs 205 arRl 206 breaks the circuit of the relay 84 to prevent the ringing-of the bells 6 after the called subscriber has line of substation A by. the connector F,

that line is protected by a guarding potential extending from ground G through side switch wiper 76, and private wiper 69 to the private bank contact 294, and thence to the corresponding contact in he bank of each of the connectors which have access to the line of substation A. A circuit also extends from the contact 294over conductor 156 and through the relay 37 and magnet 20 of switch C to battery lead 133. The relay 37, upon energizing, disconnects the line.

switch C from the line conductors 9 and 10. It should be stated here that although sufiicient current flows through relay 37 and magnet 20 to maintain the armature 21 in an operated position, it is not strong enough "to pull down the said armature from 1ts normalposition.

After a conversation is completed, the hanging up of the receiver at the called substation breaks the circuit of the connector back bridge relay 85, which de'e'nergizes and removes theshort circuit from the relay 56.

The-relay 56 thus again enters the circuit.

of the relay 91 (Fig. 2), allowing the armature of said relay to drop back and close the circuit of lamp 93. The hanging up of the receiver at the calling substation breaks the energizing circuit of the relay 92 which deenergizes and closes a circuit through the lamp 94. The simultaneous glowing of the lamps. 93 and 94 signifies to the operator that both receivers have been hung up. The

removal of the plugs p and 7) from their respective jacks breaks the circuits of the relays 90 and 89, respectively, which delinergize and extinguish the lamps 94 and 93. The removal of the plug p from the jack also breaks the circuits of the connector relays 73 and 56. The deenergization of both- 133' The magnet 81, upon energizing, rel stores the switch shaft and side switch to normal position. When the switch shaft reaches its lowest position it separates the springs 82 and 83, thus allowing the magnet 81 to become deenergized.

Returning now to that stage of the opera tion when the wipers of the connector F have been advanced to the terminals of the desired line, and before the private magnet relay 79 has deenergized, it will be explained how the operator is given the busy signal in case the called line'is busy. .It is evident that whenever a line is busy, a

guarding ground potential is present at the private bankcontact 294 of each of the connectors which have access to the line. Thus, when the private magnet relay 79 deenergizes, with the wipers resting on the contacts of a busy line, a circuit is closed extending from the guarded bank contact 294 through the side switch wiper 76 (which is now in second osition), relay springs 218 and 219, relay 220, springs 221 and 200 of the relay 79, and through the private magnet 78 to the battery lead 133. The current flowing over this circuit prevents the private magnet 78 from deenergizing, and

causes the relay 220 to be energized. In its energized position the relay 220 closes a locking circuit for itself and the magnet 78, said circuit extending from ground G? through the springs 223 and 219, and through the relay 220 and magnet 78 to the battery lead 133, as before traced.- As long as the magnet 78 thus remains energized the side switch is locked in second position and the operator receives a signal from a.

busy signaling machinesimilar to the machine L (Fi 5) through 'the-springs224 and 225 of the private magnet ;78, contact springs 148 and 149, thenceoverthe conduct'or 87 to and through the operators set and back over the trunk conductor 86, springs 146 and 147, conductor 187, and winding 188 of the relay 73 to the battery lead 133, to which the other side of the busy signalin machine is connected. The conductor F 1s released in this instance by the removal of the plug p from'the jack, just as in the previous case. The locking circuit of the relay 220 ,and magnet 78 is broken at the springs 82 and 83 when the switch shaft reaches its lowest position. 1

. point 226, side switch wiper -75, springs 210 and'209, condenser 295, conductor 186,

trip magnet 100 of the line switch C (Fig.

1) into the ack 7?, throws the key K and operates the calling device once for each digit of the number of the line wanted. The insertion of the plug 7? into the jack j completes an energizing circuit through the This circuit extends from ground G through thesprings 227 and 228, over the trunk conductor 234 to and through the operators set and .back over the conductor 235, through the springs 229 and 230, trip magnet 100 and springs 231 and 232 to the battery lead 233-, thence through the battery B to groun'dGn-f The magnet 100, upon ene1'gizi11g, relea'ses the'plunger, allowing it to enter the bank-to extend the connection to the first selectorE. The frnaster switch D operates in the same manner as explained for the master switch I) to move the plungers of the idle line switches to an idle trunk. In this case, however, the motor magnet relay 236 is energized in series with the release magnet 101, the resistance of-the relay'236 being high enough to prevent sutlicient current from flowing to operate the magnet 101.

As soon as the connection is extended to the selector E, the line relay 107 is energized and operates in the same manner as the line relay 7 3 of the connector F to close the circuit of the release relay 237. When the calling device is operated for the first digit the line relay 107 responds to the impulses.

Each time the relay 107 deenergizes it closesa circuit extending from ground G through springs 238 and 239, 240 and 241, private magnet relay 242, vertical magnet 105, side switch wiper 110 to battery lead 233, thence through battery B to ground G. The vertical magnet receivestwo impulses over the circuit just traced and operates to raise the shaft and wipers two steps. As soon'as the shaft leaves its lowest position the release magnet 113 is connected to battery through the off-normal springs 296 and 1297. The slow-acting relay 242, which is included in the energizing circuit of the vertical magnet, operates in the same manner as the rethe rotary magnet 106.

lay 79 of the connector F to cause the private magnet 112 to trip the side switch to second position. When the side switch wiper 110 engages its second-position contact point a circuit is closed through This circuit extends irom ground G through interrupter springs 244, magnet 106, and side switch wiper 110 to battery lead The rotary magnet 10G, upon energizing, operates to rotate the wipers one step, press down the 1 armature of the private magnet 112, and

' open its own circuit at the interrupter springs 244. When the circuit of the rotary magnet is thus opened itsarmature drops back, and if the first trunk is not busy, the armature of the private magnet follows it and allows the side switch to pass into third position, extending the connection to the repeater R. If, however, the first trunk of the second level is busy, the private wiper 104 finds the first contact which it engages connected to ground through the repeater of the busy trunk. Then the wiper 104 thus strikes a busy trunk a circuit is closed extending from the grounded bank contact through wiper 104, side switch wiper 111, contact point 245 and private magnet 112 to battery lead 233. The private magnet is thus energized and locks the side switch in second position. Consequently, the magnet 106 is again energized as soon as the interrupter springs 244 come into engagement after the rotary armature falls back. The magnet 106 thus continues to operate to advance the wipers step by step until the wipers find the terminals of an idle trunk whereupon the magnet 112 becomes denergized and allows the side switch to pass to third position. As soon as the wiper 110 leaves its second-position contact point it disconnects the battery from the rotary magnet 100. The movement of wipers 108 and 109 from second to third position cuts off the line relay'107 and extends the connection through to the repeater R.

When the connection is extended to the repeater the relay 114 becomes energized by a circuit extending from ground G through winding 247 of relay 114, conductor 248,

thence through selector E and line switch G to and through the operators calling device and back through switches C and E, and over conductor 249 and through winding 250 of relay 114 to'battery lead 233., The relay 114,upon energizing, operates to shift spring 251 out of engagement with spring 252 and into contact with springs 253, and to close contact between springs 254 and 255. The engagement of springs 251 and 253 closes a circuit through the'relay 116. The relay 116, upon energizing, connects the relay 115 with spring 252 of relay 114, supplies a guarding ground to the selector private bank contacts of the trunk, and closes a new energizing circuit for the release relay 237 of the selector ground G through springs 256 and 257 and over conductor 258 to the private bank contacts of the selector switches which have access to the trunk, thence over wiper l04,-side switch wiper 111 and relay 237 to battery lead 233. lhis circuit is closed before the relay 237 has time to deenergize after its former circuit is broken by the deenergization of relay .107. The engagement of the springs 254 and of relay 114 closes a bridge across the trunk conductors 259 and E. This circuit extends from' "breaks the circuit of the relay 11.6, and of 260 through the impedance coil 271. \Vhen the impedance coil 271 is thus bridged across the trunk the linerelay 261 of the selector H is energized over a circuit extending from ground Gr through winding 263 of relay 261, side switch wiper 265, conductor 260, coil 271, springs 25 1 and 255, conductor-259. 'side'switch wiper 264, and winding 262 of relay to 261 to battery lead 266,! thence through the battery B to ground G. When the calling device is operated for the remaining digits of the called number, the relay 114 responds to the impulses in the same manner as did the selector line relay 107 for the first digit. Each time the relay 114: deenergizes it separates the springs 255 and 254, thus repeating the impulses to the trunk conductors 259 and 260. Also, each time the relay 114 deenergizes, it closes a circuit extending from ground G through springs 251 and 252, 267 and 268, and relay 115 to battery lead 233. The relay 115 is energized by the first impulse for each digit, but, being'a slow-acting relay, its circuit is not opened long enough to permit it to deiinergize until after the last impulse for that digit is delivered. In its operated position, the relay 115 separates springs 269 and 270 from springs 271 and 272 respectively. It thus evident that the conductors 259 and 260 are disconnected from the condensers 1,17 and 118 and the impedance coil 271 is shortcircuited duringthetime the relay 114 is operating to repeat impulses. The relay 116;

is slow acting and consequently remains in its energized position while the relay 11 1 is operating,

The impulses for the second digit (2) are repeated, inthe manner-"described, to the line relay 261 of the second selector H. The selector H responds to the operation of relay 261,and operates in the same manner as'the first selector E to 'selectfan idle trunk leading to a connector F (Fig. 5.) The impulses for the last two digits are repeated by the repeater relay 114 to the line relay 372 of the connector F. The connector responds to thes'e impulses in essentially the same manner as the connector F to extend the connection to the called line. The ima bridge across the trunk conductors 259 i and 260 to m.intain the'line relay 372 of L the connector energized after the connection .is completed, and yet prevents the talking currents from passing from one side .of the i line to the other.

After the conversation is completed the release of the central office switches is initiated by the removal of the plug 7), as in the previous case. VVhen the plug 7) is removed from the jack it opens'the energizing circuit of the relay 114 of the re- ,peater R. The relay 114 upon deenergizing.

magnets 275 and 276 of their respective.

switches. The magnets 275 and 276, upon energizing; restore their respective switches to normal position, as explained for the connector F. vlVhen the relay 116 of the repeater R deenergizes it breaks the circuit of the release relay 237 of the selector E. The relay 237, upon deenergizing, closes ,the circuit of the release magnet 113, which operates to restore the selector mechanism to normal position. The relay 237, upon (leenergizing, also closes a circuit extending from ground G through the springs 238 and 239, 240 and 277, relay 278, bank springs 279 and 280 and release magnet 101 to the battery lead 233. The relay 278 has a coinparatively high resistance and consequently the magnet 101 is not energized over this circuit. The rela'y278 is energized, however,'and operates to close the springs 281 and 282 into engagement. As soon as the interrupter 283 reaches a position to shortcircuit the brushes 28% and 285 it connects the ground G5 with the release magnet 101 without any' interposed resistance. The magnet 101 thereupon energizes and places the mechanism of the line switch C in position to withdraw the plunger upon the deenergization of the magnet 101, when the interrupter breaks the connection between the brushes 284 and 285. It is to be un-.

derstood, of course, that although the switches, through which connection is established with the line #2220, are shown in operated position to more clearly illustrate the talking circuit, the said switches would notremain in such position if there was no plug in the jack j, as shown.

From the foregoing it will be seen that 1 provide an improved and highly etlicient semi-automatic telephone exchange system. It will be seen, for example, that the trunk lines between the main exchange and the branch exchange are of the two-Way type--v that is to say, they are of the kind which permit calling in opposite directions, as disany olher suitable equipment for extending connection thereto and ijherefroin. Also, and as previously explained, the automatic sw-iches between the calling subscribers and sh inanual switchboard can be released by the removal of the answering plugs from the of the manual boa-rd, whereby the ope 'ator can restore the non-numerical line sy l clies when the subscribers are through l" mg. It will be seen though, as was previously described, that. under certain circumstances the calling subscriber can release his nonnun1erical switch, but only in the eye t that he hangs up after the operator has o i hd awn the plug, or before the opera 'or has answered. Finally, it Will be seen that I provide a and highly efiicient form of repeater for use in a two-wire sy tem. This repeater, as shown and described,

' aas simple provision for cutting 05 or dis connecting the condensers While the irnpulses are being repeated.

, ll 11a: I claim as my invention is 1. in a telephone system, a manual board, a non-numerical switch, a telephone line ter- 3. inai'ing a said board, a telephone line terminating at said switch, a two-way trunk line extending from the said switch to the said board, nieans controllable at said board in: extending connection over said irunk line u said firsmnentioned telephone line to last-n'ientioned telephone and 'd board.

TV LT i ,L, I, ill a neiephone syseein, a rue-nay trunk, a numerical switch in which said inl': lierinniates at one end thereof, means n. 1 in ,x a -i. w 1 iul control mg ea] 5! or our sale lun e non-nu1ner1cal switch provider with means for seizin the paid one en'l of said and devices at the other end oi? said i. 1 telephone system, a two-Way trunk, er's non-numerical line switch for sid trunk to extend connection over in. one direction, and means for calling over said trunk in the other direcal ele-plume system, a two-way trunk. a subseribers line switch for seizing one end of i l in on direce n, a jack in which the other e i i l: terminates, a cord 'circu connecied with said lzrunlr for "or cxicnding connection thereto and inn lo extend a call over the sameeriliending coinieciion 'lzlieu'eio and therefrom, and potential. circuit for making the trunk bus at one end as a result of the seizure of the other end.

' 5. ln. a lele JilOIlQ system, a manual board, '11 ai'i'l'oinaiic switch and a irunlai :lior exen ling a calling: connection. to said board, 1 meal s for releasing said switch by the ipening of the manual connection at said 0. In a telephone sys'eein, a manual board including a cord terminating in a plug, an autoinaiic switch and a trunk terminating in a jack for extending a calling connection to said board, and means for releasingsaid switch by the removal oi the answering plug from the jack of the trunk on said board.

7. In a telephone system, a trunk terminaling illil jack, a manual board for one end of said trunk including a cord terminating in a plug, an automatic switch by which a calling line is ai'lion'iafiicahy connected with the other end of said trunk, and means for releasing by the hanging up of the re ceiver at "she calling substation only when the operator has Withdra V11 the plug from the jack of said trunk or -duui the operator has not answered.

8 in atelephone system, means for QS eablishing a, conmzction between a calling: and a called subscribefis line, said means including a two-Wire repeater provided with condensers the line c -cuii' thereof, i'z'ieans for coi :ollina" said repeater by a series of impulses, ineans controlled by said repeater for "epea'l; said impulses over a metallic means for aulimnal-ically culid condensers While the iu'ipulses circuit, an l fepeaied. )1 1.1 a, two-wire telephone system, a manual board, a non-numerical s sch, a telephone line ieri'ninatiug at said board, a

n therefrom over board, said s'wii'ch a non-inuncrical switch provided Q i Ease uien'bio ed eelephone W Z i ole over the two sides of the 11. In a two-wire telephone system, a two- 'ay trunk, a subscribers non-numericalline switch for seizing said trunk to extend connection over the same in one direction, and means for calling over said trunk in the other direction, said switch being controllable over the two sides of the line circuit thereof in series.

12. In a two-wire telephone system, a twoway trunk, a subscribers line switch for seizing one end of said trunk to extend a call over the same in one direction, and a manualboard at the other end of said trunk to extend connection over the same in the other direction, said switch being controllable over the two sides of the line circuit thereofin series.

13. In a two-wire telephone system, a two-way trunk, a subscribers line switch for seizing one end of said trunk to extend a call over the same in one direction, and a manual board at the other end of said trunk to extend connection thereto and therefrom, said switch being controllable over the two sides of the line circuit thereof in series.

14. In a two-wire telephone system, a manual board, an automatic switch and a trunk for extending a calling connection to said board, and means for releasing said switch by the opening of the manual connection at said board, said switch being contrunk terminating in a jack, a manual board for one end of said trunk including a cord terminating in a plug, an automatic switch by which a calling line is automatically connected with the other end of said trunk, and means for releasing by the hanging up of the receiver at the calling substation only when the operator has withdrawn the plug from the jack of said trunk or. when the operator has not answered, said switch being controllable over the two sides of the line circuit thereof in series. a

17. In a common battery telephone sys tem, a manual board, a non-numerical switch, a telephone line terminating at said board,-a telephone line terminating at said switch, a two-way trunk line extending from the said switch to the said board, means controllable at said board for extending con nection over said trunk line from said firstmentioned telephone line to said last-mentioned telephone line, means for-controlling said switch over said last-mentioned telephone line to extend connection therefrom over said trunk line and to said board, and a central source of talking and operating current for said system.

18. In a common battery telephone system, a two-way trunk, a numerical switch in which said trunkterminates at one end thereof, means for controlling said switch over said trunk, a non-numerical switch provided with means for seizing the said one end of said trunk, devices at the other end of said trunk for extending connection thereto and therefrom, and a central source of talking and operating current for said system.

19. In a common battery telephone system, a two-way trunk, a subscribers nonnumerical line switch for seizing said trunk to extend connection over the same in one direction, means for calling over said trunk in the other direction, and a central source of talking and operating current for said system. v

20. In a common battery telephone system, a two-way trunk, a subscribers line switch for seizing one end of said trunk to extend a call .over the same in one direction, a manual board at the other end of said trunk to extend connection over the same in the other direction, and a central source of talking and operating current for said system.

21. In a common battery telephone system, a two-way trunk, a subscribens line switch for seizing one end of said trunk to extend a call over the same in one direction, a manual board at the other end of said trunk to extend connection thereto and therefrom, and a central source of talking and operating current for said system.

22. In a common battery telephone system, a manual board, an automaticswitch and a trunk for extending a calling connection to said board, means for releasing said switch by the opening of the manual connection at said board, and a central source of talking and operating current for said systern.

23. In a common battery telephone system, a manual board including a cord termi-' ii ating in a plug, an automatic switch and a trunk terminating in a jack for extending a calling connection to said board, means for releasing said switch by the removal of the answering plug from the jack of the trunkon said board, and a central source of talking and operating current for said system.-

24. In a common battery telephone sys tem, a trunk terminating in a jack, a manual board for one end of said trunk including a cord terminating in a plug, an automatic switch by which a calling line is automati- 'cally connected with the other end of said .said system? r 25. In a telephone system, a two-way trunk, a numerical switch in which said trunkterminates at one end thereof, a non numerical switch provided with means for seizing one end of said trunk, means for controlling said numerical switch over said 'trunk, and means for cutting oft said numerical switch from said trunk when said non-numerical switch connects with said trunk.

26. In a telephone system, a two-way trunk, a numerical switch in which said trunk terminates at one end thereof, a nonnumerical switch provided with means for seizing the same end of said trunk, means for controlling said numerical switch over said trunk, a relay, and means for energizing said relay to cut off said numerical switch from said trunk when said non-numerical switch connects with said trunk.

27. In a telephone system, -a two-way trunk, a numerical switch in which said trunk terminates at one end thereof, a nonnumerical switch provided with means for seizing the same end of said trunk, means for controlling said numerical switch over said trunk, and means for preventing said non-numerical switch from seizing said trunk when said numerical switch is operated.

28; In a telephone system, a two-way trunk, a numerical switch in which said trunk terminates at one end thereof, a nonnumerical switch provided with means for seizing the same end of said trunk, a busy test contact with which a wiper of said nonnumerical switch is adapted to engage, a relay, and means for energizing said relay when said numerical switch is being operated to place a busy potential upon said contact to thereby prevent said non-numerical switch from seizing said trunk.

29. In a telephone system, a manual board, a two-way trunk terminating at one end in said board, a numerical switch in which the opposite end of said trunk terminates, a non-numerical switch provided with means for seizing the last-mentioned end of said trunk, means for controlling said numerical switch over said trunk, and means for cutting ofl' said numerical switch from said trunk when said non-numerical switch connects with said trunk.

30. In a telephone system, a manual board, a two-way trunk terminating at one end in said board, a numerical switch in which the opposite end of said trunk terminates, a non-numerical switch provided with means for seizing the last-mentioned end of said trunk, means for controlling said numerical switch over said trunk, a relay, and means for energizing said relay to cut off said numerical switch from said trunk when said non-numerical switch connects with said trunk.

31. In a telephone system, a manual board, a two-way trunk terminating at one end in said board, a numerical switch in which the opposite end of said trunk terminates, a non-numerical switch provided with means for seizing the last mentioned end of said trunk, means for controlling said numerical switch over said. trunk, and means for preventing said non-numerical switch from seizing said trunk when said numerical switch is operated.

32. In a telephone system, a. manual board, a two-way trunk terminating at one end in said board, a numerical switch in which the opposite end of said trunk terminates, a non-numerical switch provided with means for seizing the last-mentioned end of said trunk, a busy test contact with which a wiper of said numerical switch. is adapted to engage, a relay, and means for energizing said relay when said numerical switch is being operated to place a. busy potential upon said contact to thereby pre" vent said non-numerical switch from seizing said V trunk. I i

In a telephone system, a plurality of subscribers lines, means including a repeater for establishing a connection between two of said lines, means for controlling the operation of said repeatercver twc sides of a line circuit in. series, condensers in the line circuit of said repeater, relay, and means for energizing said relay during the operation of said repeater to cut oft said condensers from the line circuit.

34. In a telephone system, a manual board, a non-numerical switch, a telephone 1 line terminatingat said board, a telephone line terminating at said switch, a two-way trunk line extending from the said switch to the said board, means control] able at said board for extending connection over said trunk line from said fi1'st-mentioned telephone line to said last-mentioned telephone line, means for controlling said switch over said'last-mentioned telephone line to extend connection therefrom over said trunk line and to said board, and automatic means for signaling the board.

'35. In a telephone system, a two way trunk, a numerical switch in which said trunk terminates at one end thereof, means for controlling said switch over said trunk, a nonnumerical switch provided -with means for seizing the said one end of said trunk, devices at the other end of said trunk for extending connection thereto and therefrom, and automatic means for signal ing the other end.

36. Ina telephone system, a two-Way trunk, a subscribers non-numerical line switch for seizing said trunk to, extend connection over the same in one direction,

means for calling over said trunk in the other direction, and means for signaling automatically in the first direction.

37. In a telephone system, a manual board, an automatic switch and a trunk for extending a calling connection to said board,

, and means for automatically signaling the I end of said trunk including a cord terminating in a plug, an automatic switch by which a calling line is automatically connected with the other end of said trunk, and means for automatically signaling the other end of the trunk and for releasing by the hanging up of the receiver at the calling substation only when the operator has Withdrawn the plug from the jack of said trunk or when the Operator has not answered.

40. In a telephone system, a plurality of lines, an individual non-numerical trunking switch for each line, a plurality of trunks common to said switches for extending connections fromsaid lines, a common trunk selecting mechanism for locating an idle trunk line for said switches, trunking means associated with the other end of said trunk lines for extending connections in the re versed direction, an automatic progressively movable connector switch for each trunk line, said connectors controlled over said trunk lines from the said lastmentioned trunking means, for extending connections from said trunks.

41. In a telephone system, subscribers lines, a manual switchboard, non-numerical trunking switches for said lines, trunk lines extending between said switches and said board, connector numerical switches between said trunk lines and said subscribers lines, and having access to said subscribers lines, a master switch associated with said trunk lines for selecting an idle trunk line, said non-numerical trunking switches controlled over said lines for extending connection to the idle trunk line for extending connection to said manual board, means for said manual board for extending conne tion over any one of said trunk lines in the reversed direction to any one of said connector switches and for operating such .a connector over the extended connection. to

- establish a circuit with any one of said subscribers lines.

Signed by me at Chicago, Cook county,- 

